1. Field of the Invention
This invention relates to the field of human dietary supplements, and more specifically to improved supplements comprising extract preparations of the ginkgo biloba leaf, and to methods of making and administering such supplements.
2. Background
The ginkgo biloba tree is native to southeastern China, and is a member of the Ginkgoales family, which dates from the Permian Period of the Paleozoic Era. Ginkgo biloba has been a staple Chinese herbal ingredient for thousands of years, and is frequently recommended by Chinese herbal practitioners for coughs, asthma and acute allergic inflammations. Commercially prepared extracts of ginkgo biloba leaves have been used for decades as a medicinal aid, and are believed to be an important component of a food supplement program to ensure optimum nutritional health.
The commercially prepared mixtures are intended to substantially conform to an established molecular component profile, that includes a 24% flavonoid glycoside component, which comprises mostly kaempferol and quercetin glucorhamnoside esters, and 6% characteristic terpene lactones, the ginkgolides and bilobalides. A ratio of about 24% flavonoid glycosides to about 6% terpene lactones occurs in nature. [Kleijnen, J. and Knipschild, P., Br. J. Pharmac., 34:352-58 (1992)].
This standardized ginkgo biloba extract comprised of a mixture of biologically active natural products provides for a complex range of activity. For example, the flavonoids present in ginkgo biloba function as free radical scavengers which reduce the amount of harmful free radicals in the body. Free radical formation can disrupt vascular membranes, resulting in increased microvascular permeability which in turn is associated with the impairment of cerebral blood flow seen with aging. Id. The terpene lactones present in ginkgo biloba, particularly ginkgolide B, are reported to be potent inhibitors of platelet-activating factor (PAF). [DeFeudis, F. G., Ginkgo Biloba Extract (EGb 761), Pharmacological Activities and Clinical Applications (Editions Scientifiques) (Elsevier, Paris (1991))]. PAF can disrupt vascular membranes, and is known to induce platelet aggregation, neutrophil degranulation, oxygen radical production, and bronchoconstriction. It has been reoirted that by its inhibition of PAF, ginkgolide B helps improve cerebral metabolism and protect the brain against hypoxic damage in laboratory animals with cerebral ischaemia. [Kleijnen, J. and Knipschild, P., The Lancet 340:1136-39 (1992)].
In addition to limiting membrane damage, ginkgo biloba extract appears to affect vascular tone, cerebral metabolism and neurotransmitters and their receptors. See DeFeudis, F. G., cited above. Ginkgo biloba extract is licensed in Germany for the treatment of cerebral dysfunction, hearing loss resulting from cervical syndrome, and peripheral arterial circulatory disturbances with intact circulatory reserve (intermittent claudication). See Kleijnen, J. and Knipschild, P., cited above. Other studies indicate the efficacy of using ginkgo biloba extract to improve mental acuity and memory enhancement. [Clostre, F., La Presse Medicale, 15: 1529-1538 (Sep. 25, 1986); Kleijnen, J., and Knipschild, P., cited above].
Flavonoid glycosides, which are part of the bioflavonoid family, are flavonoid molecules that are unique to ginkgo. The flavonoid glycosides include kaempferol, quercetin, sciadopitysin, luteolin, amentoflavone, isohamnetin, ginkgetin, delphidenon, isoginkgetin, procyanidin, bilobeitin, and prodelphinidin. Commercially available preparations of ginkgo also contains two other classes of chemical compounds, terpene lactones (ginkgolides A, B, C and bilobalide), and minor organic acids such as hydroxybenzoic acid, hydroxykynurenic acid, pyhrocathcuric acid and vanillic acid.
In addition to the medicinally beneficial compounds, potentially toxic components of the leaf, chiefly ginkgolic acid and ginkgol, are also present, but at non-toxic levels. These potentially toxic compounds belong to the ginkgolic acid family, and, regardless of their amount, are virtually eliminated by present-day commercial extraction processes.
3. Description of Prior Art
Total synthesis of the biologically active natural products of the ginkgo biloba leaf has been accomplished. [Nakanishi and Kishi, Tet. Let. 4:299-302 (1967)]. Due to the complexity of the molecular structure of these products, however, this synthesis is not cost-effective for production to meet present day consumer needs.
Commercially available ginkgo biloba extract has been prepared using an elaborate acetone-water extraction. [Drieu, K., La Presse Medicale, 15:1455-57 (September 1986)]. However, due to environmental regulations that severely restrict the use of acetone in the United States for food manufacturing purposes, the acetone-water methodology is acutely limited for commercial processes in the United States.
There is a need in the art for a means of producing ginkgo biloba product that is not subject to the regulatory restrictions and commercial expense that characterizes the current art.